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| Titel |
Modelling the urban air quality in Hamburg with the new city-scale chemistry transport model CityChem |
| VerfasserIn |
Matthias Karl, Martin Ramacher, Armin Aulinger, Volker Matthias, Markus Quante |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250141955
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| Publikation (Nr.) |
 EGU/EGU2017-5519.pdf |
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| Zusammenfassung |
| Air quality modelling plays an important role by providing guidelines for efficient air
pollution abatement measures. Currently, most urban dispersion models treat air pollutants as
passive tracer substances or use highly simplified chemistry when simulating air pollutant
concentrations on the city-scale. The newly developed urban chemistry-transport model
CityChem has the capability of modelling the photochemical transformation of multiple
pollutants along with atmospheric diffusion to produce pollutant concentration fields for the
entire city on a horizontal resolution of 100 m or even finer and a vertical resolution of
24 layers up to 4000 m height. CityChem is based on the Eulerian urban dispersion model
EPISODE of the Norwegian Institute for Air Research (NILU). CityChem treats the
complex photochemistry in cities using detailed EMEP chemistry on an Eulerian 3-D
grid, while using simple photo-stationary equilibrium on a much higher resolution
grid (receptor grid), i.e. close to industrial point sources and traffic sources. The
CityChem model takes into account that long-range transport contributes to urban
pollutant concentrations. This is done by using 3-D boundary concentrations for the
city domain derived from chemistry-transport simulations with the regional air
quality model CMAQ. For the study of the air quality in Hamburg, CityChem was
set-up with a main grid of 30×30 grid cells of 1×1 km2 each and a receptor grid
of 300×300 grid cells of 100×100 m2. The CityChem model was driven with
meteorological data generated by the prognostic meteorology component of the Australian
chemistry-transport model TAPM. Bottom-up inventories of emissions from traffic, industry,
households were based on data of the municipality of Hamburg. Shipping emissions
for the port of Hamburg were taken from the Clean North Sea Shipping project.
Episodes with elevated ozone (O3) were of specific interest for this study, as these are
associated with exceedances of the World Health Organization (WHO) guideline
concentration limits for O3 and of the regulatory limits for NO2. Model tests were
performed with CityChem to study the ozone formation rate with simultaneous variation
of emissions of nitrogen oxides (NOx) and volatile organic compounds (VOC).
Emissions of VOC in urban areas are not well quantified as they may originate
from various sources, including solvent usage, industry, combustion plants and
vehicular traffic. The employed chemical mechanism contains large uncertainties with
respect to ozone formation. Observed high-O3 episodes were analyzed by comparing
modelled pollutant concentrations with concentration data from the Hamburg air
quality surveillance network (http://luft.hamburg.de/). The analysis inspected possible
reasons for too low modelled O3 in summer such as missing emissions of VOC from
natural sources like green parks and the vertical exchange of O3 towards the surface. |
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